One of the biggest fears of the fresh fruit industry just came true.
A fungal disease that has been destroying banana plantations in Asia has arrived in Latin America.
"For me, the worst moment was [seeing] the first pictures," says Fernando Alexander García-Bastidas, a banana researcher at the Dutch company Keygene, who carried out tests confirming what had happened.
Some farmers in Colombia, where García-Bastidas grew up, sent him photos of their banana plants two months ago. The plants were turning yellow and wilting, as if they didn't have water.
García-Bastidas recognized the symptoms. He'd seen them before, in devastated banana plantations in the Philippines. These are the effects of a fungus called Fusarium. But the implications were devastating, and García-Bastidas hoped he was wrong.
"I felt this thing in my heart that was like kind of praying for a false positive, or something like that," García-Bastidas recalls. "It was terrible" — and doubly distressing because it affected his homeland.
For the next month, he says, he had trouble sleeping. He flew to Colombia, collected samples of the wilting plants and tested them. The results confirmed his fears. The plants were infected with a variant of Fusarium fungus called Tropical Race 4, or TR4.
TR4 began marching through the world's banana-growing countries in the 1990s. First detected in Taiwan, it moved to Malaysia and Indonesia, then jumped to China, Australia and the Philippines. It showed up in Mozambique, in Africa, five years ago.
People involved in banana production or research have taken extreme measures to prevent it from spreading. When García-Bastidas visits an area where the fungus is present, he'll buy a new pair of shoes before entering another banana-growing region to avoid bringing in a speck of fungus-contaminated soil. The main international conference on banana research no longer takes place in any banana-growing country, to reduce the risk that the fungus might hitch a ride with one of the researchers.
Somehow, though, it has now hopped the ocean and arrived in Latin America. García-Bastidas says he expected it would happen someday, but not so quickly. "It's very difficult to control the spread of this disease," he says.
The Fusarium fungus lives in the soil. No one knows how to eradicate it or to treat infected plants. It invades banana plants through their roots and then blocks the vessels that carry water and nutrients, starving the plants. It kills most members of the banana family, including the variety called Cavendish that accounts for the vast majority of bananas traded internationally.
Colombian authorities have declared a national emergency and launched efforts to contain the fungus. Banana growers are destroying all banana plants anywhere near a plant that shows symptoms.
They may be too late, though. By the time symptoms appear, the fungus has already been present in the soil around that plant for at least a year. During that time, people may have been walking through the farms, perhaps picking up bits of fungus on their shoes and spreading it. "I hope I'm wrong, but most likely it spread already to other places," says García-Bastidas.
The only good news may be that the disaster will unfold slowly. It can take years or decades for the fungus to move across entire countries or continents. In Asia, individual farms have been devastated, but many of the affected countries remain major banana producers.
Meanwhile, researchers are trying desperately to find a new kind of banana that can survive Tropical Race 4.
Scientists in Australia have created a fungus-resistant variety using genetic engineering. It's still being tested and would require government approval before it could be grown or sold.
Other scientists are looking through nature's storehouse. When García-Bastidas was a graduate student at Wageningen University, in the Netherlands, he tested 300 different members of the banana family.
"Unfortunately, 80% of the [varieties] that I tested were susceptible to TR4," he says. "But there is a little bit of hope with the other ones that were not susceptible."
None of those fungus-resistant plants are ready to replace the bananas that currently fill supermarket shelves. Most of them are cooking bananas, or plantains. Others are wild bananas with tiny fruit that's inedible; the pods are full of seeds.
The hope, however, is that plant breeders can take these plants and cross-pollinate them, mating them with other, more commercially viable bananas, reshuffling the genes to create new varieties that are both delicious and immune to TR4. The company where García-Bastidas now works, Keygene, is one of the research centers pursuing this goal.
Breeding bananas is so complicated that few people have ever tried it. For one thing, it takes bananas with seed-filled fruit, since those seeds represent the new genetic combinations that plant breeders want. Yet those seeds can't appear in the fruit of a commercial variety.
García-Bastidas says the task is very difficult. But it is possible. And now it's necessary.